Compost en Paises en Desarrollo

8/12/2019 Compost en Paises en Desarrollo

1/52

Composting and Its Applicability inDeveloping Countries

Published for the Urban Development DivisionThe World Bank, Washington DC

W O R K I N G

P A P E R

S E R I E S

8

Daniel HoornwegLaura ThomasLambert Otten


2/52

ii

Copyright 1999

The International Bank for Reconstruction

and Development/THE WORLD BANK

1818 H Street, N.W.

Washington, D.C. 20433, U.S.A.

All rights reserved

Manufactured in the United States of America

First printing March 2000

Urban and Local Government Working Papers are published to communicate the

results of the Banks work to the development community with the least possible

delay. The typescript of this paper therefore has not been prepared in accordance

with the procedures appropriate to formal printed texts, and the World Bank ac-

cepts no responsibility for errors. Some sources cited in this paper may be informal

documents that are not readily available.

The findings, interpretations, and conclusions expressed in this paper are entirely

those of the author(s) and should not be attributed in any manner to the World

Bank, to its affiliated organizations, or to members of its Board of Executive Direc-

tors or the countries they represent. The World Bank does not guarantee the accu-

racy of the data included in this publication and accepts no responsibility for any

consequence of their use. The boundaries, colors, denominations, and other infor-

mation shown on any map in this volume do not imply on the part of the World Bank

Group any judgment on the legal status of any territory or the endorsement or ac-

ceptance of such boundaries.

The material in this publication is copyrighted. Request for permission to reproduce

portions of it should be sent to the Urban Development Division at the address in

the copyright notice above. The World Bank encourages dissemination of its work

and will normally give permission promptly and, when reproduction is for non-

commercial purposes, without asking a fee.


3/52

Acknowledgements ...................................................................................................................... v

Executive Summary ...................................................................................................................... 1

Introduction ................................................................................................................................... 3

Applicability in Developing Countries .............. .............. .............. ............... .............. .............. .... 3

Benefits of Composting ................................................................................................................. 4

Constraints on Composting.............. .............. .............. ............... .............. .............. .............. ........ 4

Design Requirements .................................................................................................................... 5

Residential Composting ............................................................................................................ 5

Decentralized Community Composting ................................................................................... 6

Centralized Large-Scale Composting ............. .............. .............. .............. .............. .............. .... 6Marketing Compost ....................................................................................................................... 7

Compost Quality ............................................................................................................................ 8

Environmental Issues .................................................................................................................... 9

Cost of Composting ..................................................................................................................... 11

Conclusions ................................................................................................................................. 13

Recommendations ....................................................................................................................... 14

References .................................................................................................................................. 15

Annex A. Review of Compost Programs ................................................................................ 19

Annex B. Composting Mechanics ........................................................................................... 25

Annex C. Composting Processes ............................................................................................. 33

Annex D. Composting Health and Safety .............................................................................. 41

iii


4/52

iv

Tables:

Table 1. Concentration of heavy metals in different composts....................................................8

Table 2. Environmental costs and benefits of composting ........................................................12

Table B1. Turning frequency based on system intensity ..............................................................26

Table B2. Nitrogen content and C/N ratios of compostable materials ........................................27

Table B3. Typical temperature classifications for microorganisms .............................................28

Table B4. Thermal kill of pathogens and parasites ......................................................................30

Table C1. Comparison of composting processes .........................................................................36

Table D1. Relative health hazards of various compostable materials ..........................................41

Table D2. Indicator pathogenic organisms and pathogens inbiosolids, hospital waste, and MSW ............. .............. .............. ............... .............. ...... 42

Table D3. Global compost standards as of April 1996.................................................................43

Figures:

Figure 1. Environmental impact of composting versus landfilling ............................................10

Figure B1. Composting inputs and outputs ...................................................................................25

Figure B2. Microorganism growth profile during composting process ............. .............. ............. 28

Figure B3. Temperature variation during composting process ............. .............. .............. ............ 29

Figure C1. Individual turning a windrow ......................................................................................33

Figure C2. Chinese covered pile method .......................................................................................34


5/52

THE WORLD BANK URBAN AND LOCAL GOVERNMENT

COMPOSTINGANDITSAPPLICABILITYINDEVELOPINGCOUNTRIES

URBAN WASTE MANAGEMENT

ACKNOWLEDGEMENTS

Valuable comments on this paper were received by David Wilson and Jane Olley, ERM Consult-

ants, and Luis Diaz, CalRecovery Ltd., and Prof. Mel Finstein of Rutgers University. In addition,

Prof. Finstein contributed the discussion on centralized composting processes in Annex C.

World Bank reviewers included Panneer Selvam, Fred Wright, and Carl Bartone. Figures were

prepared by Diane Duncan, School of Engineering, University of Guelph. Mercedes Aleman and

Laura DeBrular assisted with the formatting and final editing of this publication.

v


6/52

vi


7/52

1

EXECUTIVE SUMMARY

Composting has always existed on every field and forest floor, and intuitively it makes sense to

compost the organic fraction of the municipal solid waste stream. Composting is a cornerstone of

sustainable development, yet it is often neglected within integrated municipal solid waste manage-

ment programs. This informal paper argues that composting should be a more widespread practice,

especially in developing countries. Composting is obviously not a panacea to todays vexing waste

management problems, but it should be an important component within most integrated municipal

waste management strategies.

Over 50 percent of an average developing country citys municipal solid waste stream could be

readily composted. Composting is a simple process where optimization efforts are used to increase

the rate of decomposition (thereby reducing costs), minimize nuisance potential, and produce aclean and readily marketable finished product. Composting helps to increase the recovery rate of

recyclable materialshousehold source separation of recyclable paper, metal and glass is already

common in many developing countries.

Composting provides many benefits:

increases overall waste diversion from final disposal, especially since as much as 80% of

the waste stream in low- and middle- income countries is compostable

enhances recycling and incineration operations by removing organic matter from the

waste stream

produces a valuable soil amendmentintegral to sustainable agriculture

flexible for implementation at different levels, from household efforts to large-scale

centralized facilities can be started with very little capital and operating costs

addresses significant health effects resulting from organic waste, such as reducing

Dengue Fever

provides an excellent opportunity to improve a citys overall waste collection program

can integrate existing informal sectors involved in the collection, separation and recycling

of wastes

Composting is not more wide-spread for a number of reasons. These include: inadequate attention

to the biological process requirements; lack of vision and marketing plans for the final compost

product; poor feed stock which yields poor quality finished compost; poor accounting practices

which neglect that the economics of composting rely on externalities, such as reduced soil erosion,

water contamination, climate change, and avoided disposal costs; sensible preoccupation by mu-nicipal authorities to first concentrate on providing adequate waste collection; inadequate pathogen

and weed seed suppression; nuisance potential, such as odors and rats; poor marketing experiences;

poor integration with the agricultural community; and land requirements are often minimal, but

can be a constraint. All of these constraints can be overcome. This paper reviews past composting

experiences and provides an outline for municipal managers to use when evaluating composting

programs within an integrated municipal waste management system.


8/52

2


9/52

3

INTRODUCTION

Composting has always existed on every field and forest floor, and intuitively it makes sense to

compost the organic fraction of the municipal solid waste stream. Composting is a natural process

which provides several benefits: the process can be inexpensive; it addresses over 50 percent of a

citys waste stream; it reduces one of the worlds largest contributors to Greenhouse gases; it en-

hances related recycling and incineration activities; and it can produce a beneficial end product with

unlimited marketing potential. It simply recycles organic material back to the topsoil from where it is

mined through typical agricultural practices.

Composting is a cornerstone of sustainable development, yet it is often neglected within integrated

municipal solid waste management programs. This informal paper argues that composting should

be a more widespread practice, especially in developing countries. However, composting can only

be part of municipal solid waste programs if adequate recognition is given to the need and costs

associated with proper waste disposal; nothing is cheaper than not collecting solid waste.

Composting is obviously not a panacea to todays vexing waste management problems; but it should

be an important component within most integrated municipal waste management strategies. This

paper views the role of composting from the perspective of a municipal solid waste manager; an

equally relevant perspective would be that of the agriculturist.

To identify common themes, examples of both successful and failed initiatives are provided in

Annex A. Annex B (Composting Mechanics), Annex C (Composting Processes), and Annex D

(Composting Health and Safety), are provided as brief introductions to these issues in the hope of

encouraging more evaluation of composting proposals by municipalities.

Over 50 percent of an average citys municipal solid waste stream in a developing country could be

readily composted. Composting is a relatively simple process; the compost operator helps nature

take its natural course. Optimization efforts increase the rate of decomposition (thereby reducing

costs), minimizes nuisance potential, and promotes a clean and readily marketable finished prod-

uct. Composting is highly compatible with other types of recycling. Diverting organic materialhelps to increase the recovery rate of recyclable materials, while at the same time, recycling pro-

grams for glass and plastics, which are common Municipal Solid Waste (MSW) compost contami-

nants, improve the quality of the finished compost. Household source separation of recyclable

paper, metal and glass is already common in many developing countries.


10/52

4

Many cities in developing countries are plagued with poor waste collection. While a few, more

influential residents may get daily waste collection, others may never have such services. Daily

waste collection in wealthy neighborhoods is usually too frequent and contributes to the lack of

collection in poorer areas. In more affluent areas of a city, the use of containers and diversion of

organic waste for composting is a good way to quickly improve the cities overall waste collection

service. Many cities have switched from unreliable daily collection to bi-weekly organic waste

collection and weekly non-organic waste collection. Variations of this schedule are easily tailored

to each areas individual characteristics. Introducing waste diversion for composting programs

provides a city with a unique opportunity to improve its overall waste collection service.

increases overall waste diversion from final disposal, especially since as much as 80% of thewaste stream in low- and middle- income countries is compostable

enhances recycling and incineration operations by removing organic matter from the

waste stream

produces a valuable soil amendmentintegral to sustainable agriculture

promotes environmentally sound practices, such as the reduction of methane generation

at landfills

enhances the effectiveness of fertilizer application

can reduce waste transportation requirements

flexible for implementation at different levels, from household efforts to large-scale

centralized facilities

can be started with very little capital and operating costs

the climate of many developing countries is optimum for composting addresses significant health effects resulting from organic waste, such as reducing

Dengue Fever

provides an excellent opportunity to improve a citys overall waste collection program

accommodates seasonal waste fluctuations, such as leaves and crop residue

can integrate existing informal sectors involved in the collection, separation and recycling

of wastes

inadequate attention to the biological process requirements

over-emphasis placed on mechanized processes rather than labor intensive operations lack of vision and marketing plans for the final compost product

poor feed stock which yields poor quality finished compost, for example heavy metal

contamination

poor accounting practices which neglect that the economics of composting rely on externalities,

such as reduced soil erosion, water contamination, climate change, and avoided disposal costs

difficulties in securing finances since the revenue generated from the sale of compost will

rarely cover processing, transportation and application costs


11/52

5

subsidies may be required to maintain programs; these reflect the benefits that accrue beyond

local governments, and avoided disposal costs are not adequately addressed

sensible preoccupation by municipal authorities to first concentrate on providing adequate

waste collection

inadequate pathogen and weed seed suppression

nuisance potential, such as odors and rats

poor marketing experiences

poor integration with the agricultural community

perverse incentives such as fertilizer subsidies or over-emphasis on capital intensive projects

land requirements are often minimal, but can be a constraint

All organic matter will eventually decompose, however, some materials are more suitable for

composting than others. The raw materials which are most appropriate for composting include:

vegetable and fruit waste; farm waste such as coconut husks and sugar cane waste; crop residues

such as banana skins, corn stalks and husks; yard waste such as leaves, grass and trimmings;

sawdust; bark; household kitchen waste; human excreta and animal manure. All of these organic

materials are readily found in municipal solid waste generated in developing countries. Animal

waste, such as carcasses and fish scraps, can be used as well but they are more likely to attract

unwanted vermin and generate odors. Other organic matter such as wood, bones, green coconut

shells, paper and leather decompose very slowly and hinder the composting process (Lardinois and

van der Klundert, 1993).

Composting occurs whenever there is sufficient oxygen, water and ambient temperatures. Design-ing a composting system usually involves optimization between: transportation, land, labor, and

capital costs, feedstock, and markets. There is never one right answer but rather several possible

options. For example, combinations of community and large-scale composting facilities should be

encouraged to reduce municipal costs.

Household composting can be a simple way to manage kitchen and garden wastes. This type of

composting effectively reduces waste quantities for collection, thereby improving efficiency and

reducing operating costs. Residential composting should be promoted when a significant number

of homes have individual or collective yards or gardens and there is sufficient space (UNEP, 1996).

Composting units can be made out of locally available materials such as wood, bamboo, clay bricks,wire mesh, etc. The design and operation of the composters should not attract rodents, insects, or

other scavenging animals. Keeping large quantities of meat, fish and fatty food out of the composter

is the best way to keep pests away from the unit.

Public health officials may discourage household composting because of perceived health risks,

however, local governments can overcome this concern through public awareness programs,


12/52

6

providing subsidies for basic composting units, and promoting education on compost processes,

e.g., how to minimize the presence of rodents and flies.

Decentralized composting at a neighborhood or community scale provides small groups a way to

compost at a relatively low cost. Households, commercial establishments (e.g., small markets or

shops), and institutions (e.g., government buildings, schools) in an area generating between five

and 50 tonnes of organic waste per day can compost on vacant land, beside community gardens, or

in public parks. Local governments can support the project through public education, providing

land for the facility, assisting with start-up costs, transporting and disposing of rejects to local

landfills, and using the final compost in public parks. To ensure that the composting operation is

environmentally and socially acceptable, UNEP (1996) recommends the following requirements

for the site: the site be accessible to all individuals who want to use it

the site be clearly designated with signs which all users and non-users can understand

the site have approval from all surrounding land users

the site have adequate controls to prevent it from becoming an area for local dumping

the site have appropriate soil and drainage to accommodate the leachate

Centralized composting can range from 10 tonnes per day to more than 500 tonnes per day. Since

centralized composting is on a significantly larger scale, environmental, social and technical con-

siderations should be approached in a more formal manner and address the following requirements

(UNEP, 1996): technical assessment of the area, soil, and geographic characteristics of potential sites

inclusion of engineering and design professionals in site selection and facility design

environmental assessment of the site

formal evaluation and site selection processes that involve all relevant stakeholders

program to minimize and/or compensate for nuisance effects of traffic, odor, leachate, and

noise produced by the composting operations

separate collection and/or pre-processing system to ensure that unwanted materials do not

enter the composting system; special attention paid to the informal sector in pre-processing the

waste and recovery of non-compostable materials

establishment of a marketing strategy for the compost

enforceable protocols for the quality and composition of the compostable materials delivered to

the facility formal agreements made between all municipalities within the jurisdiction for siting, design,

financing, operations, maintenance, environmental compliance, and billing for services and

waste delivery

designated routes for the delivery of organic materials to the facility


13/52

7

Even though organic decomposition is a natural process, health and safety issues exist for workers

and neighboring residents that need to be addressed. Establishing compost standards and taking

precautions in the facility design and operations should assist in the mitigation of any negative

health and safety impacts. These issues and suggestions are presented in Annex D.

Virtually any soil will benefit from the application of compost. Theoretically, there is an unlimited

market for good quality compost; the organic matter is simply recycled back to where it came from.

However, the cost of production, transportation and application of compost can exceed the benefits.

Therefore, good marketing programs, and optimizing the use of compost, needs to be the basis of a

successful municipal compost project. The issue of compost marketing is not so much finding a use

for the finished compost but rather finding cost-effective applications. The history of many failedcomposting projects can be attributed to poor marketing strategies and inadequate attention to long-

term financing.

The first step in developing a marketing strategy is to assess all existing and potential markets.

This requires knowledge of the product, potential uses, limitations on use, and estimating the value

of the product to the user. It is also important to adapt the marketing strategy to meet the local

requirements by considering soil characteristics, agricultural practices, social customs, climate,

transportation costs, seasonal variations, etc. The other critical aspect of a compost marketing

strategy is to adequately include avoided collection and disposal costs that would be paid if the

organic matter was not composted.

The strategy has to be flexible to accommodate market fluctuations and frequently reviewed toanticipate and make the appropriate adjustments. Marketability of the finished compost is affected

by the following factors:

condition and fertility of local soils

government policies toward import substitution, such as import restrictions or subsidies on

chemical fertilizers

availability and cost of other soil conditioners, such as animal wastes and crop residues

transportation costs

local agricultural and horticultural practices

reliability and quantity of compost production

availability and cost of other agricultural inputs, including chemical fertilizers

seasonal agricultural patterns

compost quality, such as the nutrients, particle size and maturity seasonal variations in the waste stream, particularly in terms of the volume of organic waste

and its composition


14/52

8

The high organic content in the MSW stream of developing countries is ideal for composting.

However, the municipal waste stream also contains increasing quantities of glass, plastics, metals

and hazardous materials which can contaminate the finished compost. Separating contaminants

from the raw material at the compost site is inefficient since it requires additional effort, space, and

time, and it is likely that much of the contamination has already affected the organic fraction.

Source separating the waste before collection is usually an environmentally and technically better

way to improve the quality of the final compost.

In addition to ensuring a safe product, compost standards provide a valuable marketing tool. The

consumer can be satisfied with the knowledge that the product quality is consistent and suitable for

the desired application. This is important for commercial and agricultural operations where arelationship exists between predictable results and repeated sales. The supply of compost must also

be reliable since inability to meet market commitments affects customer relations and reflects poorly

upon the credibility of the program (Albrecht, 1989).

Table 1 presents indicative heavy metal concentrations in different MSW composts and demon-

strates that source separated municipal wastes produce a higher quality end product compared to

non-source separated municipal solid waste. Source separation simply means putting waste out for

collection in separate containers.

Heavy metal Source separated Source separated Non-source ProposedMSW compost: MSW compost: separated MSW standards for

Europe and North Java, Indonesia compost: MSW compost in

America Netherlands developing countries

Arsenic - 0.5 - 10

Cadmium 1.2 0.9 7.3 3

Chromium 27.0 20.0 164.0 50

Copper 59.0 54.0 608.0 80

Lead 86.0 99.0 835.0 150

Mercury 0.9 0.9 2.9 1

Nickel 17.0 50.0 173.0 50

Zinc 287.0 236.0 1567.0 300

(World Bank, 1997a)See Annex D for a discussion on the development of proposed compost standards.

Developing countries should exercise caution if applying industrialized country compost standards

because these measures are site specific and may be inappropriate. The compost standards in Table 1

were recommended by the World Bank (1997a) for Indonesia and could be applied to other develop-

ing countries.


15/52

9

The proposed compost guidelines for Indonesia were created to meet all environmental regulations

throughout the country and to assure the public that the compost is safe for use. The guidelines do

not propose a stringent and expensive testing regime, rather they have been developed to encourage

clean composting that will maximize market development and minimize future process changes.

Assumptions and factors used to set high quality compost standards for unlimited applications

include:

heavy metals should be safe for use under all soil conditions

compost product has to be of quality such that no leaching, or plant uptake, of heavy metals

will occur even under acidic soil conditions

prevent the accumulation of heavy metals even after repeated applications, which could occur

on horticultural lands proximate to cities

guarantee all future land use options with sufficient standards so that site-specific controls,

even after many years of application, are unnecessary

limited to only one class since laboratory testing facilities are usually too limited to ensure thequality of two compost classes

prevent the gradual pollution of relatively clean lands

conservative since testing costs tend to reduce testing frequency to an absolute minimum

sufficiently stringent to promote development of composting procedures and systems design

that can be exported to other countries

encompass all soil amendments, such as worm castings from vermicomposting operations

It is also suggested that the standards be re-evaluated after five years of experience with MSW

composting in different communities. If the standards cannot be achieved continuously at different

locations, the reasons for exceeding the limits should be identified and, if possible, mitigated.

Heavy metal standards may not be needed if the compost is going to be used in non-agricultural

land uses, e.g., rehabilitation of mine sites or landfill cover. However, it is prudent to design awaste management system that has the potential to produce good quality compost with unlimited

marketing potential. With proper attention to source separation and compost process control, these

standards can readily be achieved in most cities.

Similar to heavy metal standards, a review of the proposed process is critical for ensuring pathogen

and weed-seed suppression. Generally if the compost material has been exposed to temperatures in

excess of 55oC for three consecutive days, pathogens will be sufficiently reduced. In developing

countries, where reliance on laboratory tests and restrictions on compost use should be minimized,

waste management authorities should focus on the provision of a sound compost process, with

quality and temperature controls.

The emission of landfill gases (LGs) produced by the anaerobic and aerobic decomposition of or-

ganic matter is a major source of Greenhouse gases (GHG) which are responsible for global warm-

ing and ozone depletion. There is significant variation in the amount of carbon present in different


16/52

10

municipal solid waste streams. However, it is reasonable to assume that one million tonnes (Mt) of

unsorted MSW contains approximately 0.3 Mt of carbon in various forms. Experimental research

and process modeling demonstrate that about 0.2 Mt would be converted to landfill gases (LGs)

consisting of 0.09 Mt carbon dioxide and 0.09 Mt methane, and other trace constituents. LG

emissions from landfills account for nearly half of the worlds total anthropogenic sources of meth-

ane. Furthermore, methane is between 19 and 21 times more potent as a GHG than is carbon

dioxide.

It is therefore not surprising that eliminating methane emissions from MSW can substantially

lower the worlds overall GHG emissions. Although beneficial, recovering methane from landfills

has proven to be only partially successful since up to 60% of the methane generated escapes through

leakage. It is clearly much better to prevent landfilling of organic waste in the first place.

Composting is one of the simplest ways to prevent emissions of methane because the organic frac-

tion of the waste stream is diverted from landfill. While composting does release carbon dioxide, it

is currently considered to be a neutral process since the removal of carbon dioxide from the atmo-

sphere by photosynthesis to produce organic matter is also not considered.

Landfill leachate is created when water percolates through the waste and biological and chemical

constituents from the waste is brought into solution. Depending on the landfill design and prevail-

ing weather conditions, composting may not significantly reduce the quantity of landfill leachate,

but it will improve the quality of the leachate. This is achieved by reducing the concentrations of

biochemical oxygen demand (BOD) and phenols produced as a byproduct from the decomposition

of leaves and metals mobilized by the formation of carbonic acid from the decomposing organics.Composting may also produce leachate, potentially high in BOD and phenols, which should not be

discharged into water bodies. Collecting and re-circulating the leachate into active compost piles

will mitigate any environmental impacts while at the same time enhance the compost process (the

composting process is usually a net-water user).


17/52

11

In developing countries, organic matter constitutes a significant portion of municipal solid waste.

Diversion of organic materials from landfilling extends the life of the landfill by reducing the

amount of waste to be disposed.

Odors are produced when conditions inside the compost pile become anaerobic through a lack of

oxygen. A well operated composting facilities should produce minimal objectionable odors.

The final compost product can be beneficially used as a soil amendment. Recycling organic matter

back into agricultural applications improves overall soil conditions by:

developing and maintaining structure

improving physical properties

decreasing susceptibility to erosion

encouraging microbial activity

providing potentially available plant nutrients (Hesse,1984)

The effects of chemical fertilizers compared to compost are often misunderstood. The main differ-

ence between the two is that the nutrients contained in the chemical fertilizer are used rapidly but

incompletely, whereas the nutrients supplied by the compost are used slowly and stored in the soil

over an extended period (Kumazawa, 1984). Chemical fertilizers are generally preferred over

compost because they are easy to handle, store, and apply, and because they often receive economic

subsidies from governments. However, a synergistic relationship exists between compost and chemi-

cal fertilizers, and greater fertilizer efficiency can be established through the use of compost in

conjunction with chemical fertilizers (World Bank, 1997a).

Application of compost to agricultural soils may also help to suppress certain plant pathogens and

reduce the incidence of disease. The Institute Pertanian Bogor in Indonesia found that compostsignificantly reduced the occurrence of certain plant root diseases of economic importance, namely

seedling disease of chili peppers, tomatoes, and sweet corn, and wilt disease of soybeans (World

Bank, 1997a).

Composting rarely generates profits on its own. However, when viewed as a component of an

integrated solid waste management program, composting can provide economic benefits on a much

larger scale. The costs of composting includes raw materials, production, marketing, and hidden

environmental costs; whereas the benefits involve the market value of the compost, savings from

avoided waste disposal costs, as well as various positive environmental impacts.

When considering the large quantities of organic matter generated in developing countries, govern-

ments can save money by reducing the amount of waste requiring collection, transport, and dis-

posal. The extent of these savings are dependent on how the waste management system incorpo-

rates composting initiatives, including the elimination of temporary dumping sites, rerouting of

collection vehicles, and the redirection of labor.


18/52

12

Traditional cost accounting systems usually do not include the hidden costs and benefits of environ-

mental and social externalities since they are difficult to quantify. Table 3 presents some of the

environmental costs and benefits of composting which are rarely accounted for.

Costs Benefits

potential odor emissions reduced landfill space

improper disposal of rejects reduced surface and groundwater contamination

reduced methane gas emissions

more flexible overall waste management system

reduced transportation costsenhanced recycling of materials such as paper, metal and glass

reduced erosion and improved efficiency of synthetic fertilizers

reduced air pollution from burning waste

There are other benefits which may not directly impact the operation of the composting facility but

do affect the overall health and well being of society. Water contamination can occur from leachate

infiltration or from disposing of waste into open water bodies. Poor water quality has been linked

to various human infections and diseases. Each year, according to the World Health Organization

(WHO), about 900 million people experience diarrhea or contact diseases such as typhoid and

cholera spread by contaminated water. Providing alternative waste treatment options, such as

composting, will reduce the quantities of waste blocking rivers, canals and drains, and stagnantwater where mosquitoes prefer to breed and potentially transmit diseases, such as malaria and

Dengue fever.

Residents often burn their waste, contributing significantly to urban air pollution which can lead to

respiratory illnesses such as chronic bronchitis. A 1991 emissions inventory prepared by the Indo-

nesian Environmental Control Agency (BAPEDAL) estimated the share of total air pollutants at-

tributed to solid waste burning. In Jakarta about 8 percent of particulate matter and 8 percent of

hydrocarbons originated from solid waste. Bandung experienced even higher levels of 20 and 17

percent, respectively (Kozak and Sudarmo, 1992. Cited in World Bank, 1994).

Applying compost as an amendment to agricultural land for improvement of soil properties and

erosion reduction is another benefit which is rarely considered. The costs of soil erosion are notreflected in conventional measures of economic welfare because:

markets rarely exist for soil resources

influence of externalities on the true costs of soil erosion

systems of national accounts are biased to treat natural resources as free goods (Magrath and

Arens, 1989)


19/52

13

Box 1: Cost of soil erosion on Java, Indonesia

Soil degradation occurs gradually as soil depth declines by erosion and leaves progres-sively less topsoil and a lower nutrient supply. Erosion leads to decreased agriculturalproductivity and profitability, and the deposition of soil at downstream locations reducesthe benefits of infrastructure, such as reservoirs and irrigation systems. Magrath andArens (1989) estimated that for the island of Java, soil erosion costs the economy between$340 and $406 million per year; on-farm losses of productivity account for $315 million anddownstream damages cost $25 to $80 million (1989 $ values).

Because of these hidden costs, benefits and savings, MSW composting should not be evaluated

solely by the sale of finished compost. The traditional cost accounting approach used by some

municipal authorities has resulted in the closure of several compost operations established in the

past (Selvam, 1996).

Composting is all too often implemented for the wrong reasons. It will not make large profits, nor

will it solve all solid waste management problems. Incentives, such as the availability of govern-

ment subsidies and soft loans, are frequently used to set up composting projects which cannot be

sustained on a long-term basis. Composting should be considered as part of an integrated solid

waste management strategy with appropriate processing technologies selected based on market

opportunities, economic feasibility, and social acceptance. Cost effective and sustainable composting

is possible within the context of an integrated solid waste management strategy. Participation and

cooperation from many stakeholders is required, including national governments, municipalities,local communities, waste generators, and the private sector.

To enhance municipal composting efforts the following are required: (i) improved policies, (ii)

capacity building-technical and managerial, (iii) increased public education, (iv) proper full cost

accounting, (v) integration with agricultural and horticultural activities, and (vi) more focus on

implementation and day-to-day operations.

Governments should support and encourage community based, private sector, and municipal

composting initiatives by:

providing technical assistance on composting techniques

developing guidelines for the implementation of low-cost facilities

evaluating loans and other financial support allocating land for compost facilities on a long term lease basis

establishing and enforcing compost quality standards

regulating and monitoring the performance of compost operations

promoting the use of compost through public awareness campaigns

using compost in its own departments, such as public works and agriculture

reducing subsidies on chemical fertilizers


20/52

14

Source separate compostable materials from

the waste stream

Encourage small-scale decentralized

composting projects

Use labor intensive composting processes

first

Conduct an in-depth market study for the

compost end product

Study existing and past composting projects

Establish compost quality standards

Provide incentives to encourage implemen-

tation and operation of composting projects

Integrate composting within the existing

solid waste management system

Involve community based and non-

governmental organizations

Encourage public participation and input

Assess public needs and willingness to

participate

Educate all stakeholders about the benefits

of composting

Do not compost mixed municipal solid waste

Do not initially establish large-scale

composting facilities

Do not rely on highly mechanized

composting processes

Do not assume that the compost end

product will have an immediate use

Do not choose technology which is

unreliable and not replicable

Do not assume that international compost

standards are appropriate for the end use

Do not provide funding without monitoring

the implementation and performance of the

composting project

Do not assess composting success solely on

a municipal financial basis

Do not rely on enzymes or special

inoculates to enhance the process


21/52


15



REFERENCES

Albrecht, R., 1989. How to Succeed in Compost Marketing. The Biocycle Guide to Composting Municipal

Wastes. The JG Press, Inc., Emmaus, Pennsylvania, USA, pp. 118-119.

Alternative Technology Group (GTA), 1992. The SIRDO From Mexico. Los Alamos, San Mateo,

Naucalpan, Edo. de Mexico.

Asomani-Boateng, R., Haight, M. and C. Furedy, 1996. Community Composting in West Africa. Biocycle,

January. pp. 70-71.

Bennett, C., Bloom, D.E., Bloom, L.R., Robinson, M.S., and M.H. Simpson, 1992. Enterprises For the

Recycling and Composting of Municipal Solid Waste in Jakarta, Indonesia. Development Discus-

sion Paper No. 433, Centre for Policy and Implementation Studies, Jakarta, Indonesia, October.

Chesapeake Occupational Health Services, 1991. Health Surveillance Program for Compost Workers: An

Epidemiologic Review. WSSC Site II. Silver Spring, Maryland. Cited in Epstein, E., 1996.

Protecting Workers at Composting Facilities. Biocycle, September, pp. 69-77.

de Bertoldi, M., 1993. Compost Quality and Standard Specifications: European Perspective. Science and

Engineering of Composting: Design, Environmental, Microbiological and Utilization Aspects,

International Composting Research Symposium, Columbus, Ohio, 1992. Cited in World Bank,

1997. The Use of Compost in Indonesia: Proposed Compost Quality Standards. Infrastructure

Operations, Country Department III, East Asia and Pacific Region, June.

de Bertoldi, M., Vallini, G., and A. Pera, 1983. The Biology of Composting: A Review. Waste

Management and Research, 1, pp. 157-176.

de Bertoldi, M., Zucconi, F., and M. Civilini, 1988. Temperature, Pathogen Control and Product Quality.

Biocycle, February, pp. 43-50.

Economist, 1998. A Survey of Development and the Environment. March 21st.

Epstein, E., 1996. Protecting Workers at Composting Facilities. Biocycle, September, pp. 69-77.

Finstein, M.S., Miller, F.C. and P.F. Strom, 1986. Waste Treatment Composting as a Controlled System.

Chapter 10 in Rheem, H.J. and G. Reeds (eds), 1986, Biotechnology, vol. 8. Weinheim,

FRG: VCH Verlagesellshaft (German Chemical Society), pp. 363-398.

Hesse, P.R., 1984. Potential of Organic Materials for Soil Improvement. Conference paper in Organic

Matter and Rice. International Rice Research Institute, Manila, Philippines.

Indian Supreme Court, 1999. Solid Waste Management in Class 1 Cities in India. Report of the

Committee Constituted by the Honourable Supreme Court of India.

Johannessen, Lars Mikkel, 1999. Guidance Note on Recuperation of Landfill Gas from Municipal Solid

Waste Landfills. The World Bank, Urban and Local Government Working Paper Series, No. 4.


22/52


16



Kozak, J.H. and R.P. Sudarmo, 1992. An Overview of Air Pollution in Jakarta. Report of the EMDI

Project, Jakarta, Indonesia. Cited in World Bank, 1994. Indonesia: Environment and

Development. Washington, D.C., USA.

Kumazawa, K., 1984. Beneficial Effects of Organic Matter on Rice Growth and Yield in Japan.

Conference paper in Organic Matter and Rice. International Rice Research Institute, Manila,

Philippines.

Langouche, D.M., 1988. Organic Recycling and Biofertilizers in Agro-Chemicals News in Brief.

FADINAP/ARSAP, Agriculture Division, Economic and Social Commission for the Asia and

Pacific (ESCAP), United Nations, Bangkok, Thailand, September.

Lardinois, I. and A. van de Klundert, 1993. Organic Waste: Options for Small-Scale Resource Recovery.

TOOL, Amsterdam and Waste Consultants, Gouda, The Netherlands.

Lardinois, I. and A. van der Klundert, 1994. Recycling Urban Organics in Asia and Africa. Biocycle, June,pp. 56-58.

Magrath, W. and P. Arens, 1989. The Costs of Soil Erosion on Java: A Natural Resource Accounting

Approach. Environment Department Working Paper No. 18, World Bank, Washington. D.C.,

USA, August.

Malmros, P. and C. Petersen, 1988. The Working Conditions at Danish Sorting Plants. ISWA 88 Proceed

ing of the 5th International Solid Waste Conference, 1:487-491, Copenhagen, Denmark. Cited in

Epstein, E., 1996. Protecting Workers at Composting Facilities. Biocycle, September, pp. 69-77.

Mazumdar, I., 1992. India. Warmer Bulletin 34, August, p. 3.

Mehta, K., 1992. City Waste Management in India. Warmer Bulletin, May, p. 18.

Obeng, L.A. and F.W. Wright, 1987. The Co-composting of Domestic Solid and Human Wastes. Integrated

Resource Recovery. Technical Paper No. 57, World Bank, Washington, D.C., USA.

Pahren, H.R., 1987. Microorganisms in Municipal Solid Waste and Public Health Implications. CRC

Critical Reviews in Environmental Control 17 (3), pp. 187-228. Cited in Epstein, E., 1996.

Protecting Workers at Composting Facilities. Biocycle, September, pp. 69-77.

Perla, M., 1997. Community Composting in Developing Countries. Biocycle, June, pp. 48-51.

Richard, T., Woodbury, P., Berslin, V. and S. Crawford, 1993. MSW Composts: Impacts of Separation on

Trace Metal Contamination. Composting Frontiers, Volume 1, 3, Maplewood. Cited in World

Bank, 1997. The Use of Compost in Indonesia: Proposed Compost Quality Standards.Infrastructure Operations, Country Department III, East Asia and Pacific Region, Washington,

D.C., USA, June.

Riffaldi, R., Levi-Minzi, R., Pera, A., and M. deBertoldi, 1986. Evaluation of Compost Maturity by Means

of Chemical and Microbial Analyses. Waste Management and Research (4), pp. 387-396.


23/52


17



Rylander, R., 1993. A Perspective on Indoor Air Microbiological Contamination. pp. 334-337. Cited in

C.B.A.C.C.E. Sterling (ed.). American Society of Heating, Refrigeration and Air Conditioning

Engineers. Cited in Epstein, E., 1996. Protecting Workers at Composting Facilities. Biocycle,September, pp. 69-77.

Rynk, R. (ed.), 1992. On-Farm Composting Handbook. Northeast Regional Agricultural Service, Ithaca,

New York, USA.

SEEDS, 1984. Community Management of Waste Recycling: The SIRDO-Mexico. Pamphlet No. 8, New

York, USA.

SEEDS, 1997. Empowering the Next Generation: Girls of Maqattam Garbage Settlement. Pamphlet No.

19, New York, USA.

Selvam, P., 1996. A Review of Indian Experiences in Composting of Municipal Solid Wastes and a Case

Study on Private Sector on Private Sector Participation. Conference of Recycling Waste forAgriculture: The Rural-Urban Connection. Washington, DC, USA, September 23-24.

Solid Waste Management and Resource Mobilization Center, 1988. Instruction Manual for the Operation of

the Compost Plant Teku (Production Unit). Kathmandu, Nepal. Cited in Lardinois, I. and A. van

de Klundert, 1993. Organic Waste: Options for Small-Scale Resource Recovery. TOOL,

Amsterdam and Waste Consultants, Gouda, The Netherlands.

Tchobanoglous, G., Theisen, H. and S. Vigil, 1993. Integrated Solid Waste Management: Engineering

Principles and Management Issues. McGraw-Hill, Inc., New York, USA.

United Nations Environment Programme (UNEP) International Environmental Technology Centre (IETC),

1996. International Source Book on Environmentally Sound Technologies for Municipal Solid

Waste Management. IETC Technical Publication Series, Issue 6.

White, S., 1996. Vermiculture Bioconversion in India. Biocycle. June, pg. 65.

World Bank, 1994. Indonesia: Environment and Development. Washington, D.C., USA.

World Bank, 1997a. The Use of Compost in Indonesia: Proposed Compost Quality Standards.

Infrastructure Operations, Country Department III, East Asia and Pacific Region, Washington,

D.C., USA, June.

World Bank, 1997b. Brazil: Managing Pollution Problems, The Brown Environmental Agenda, Volume II-

Annexes. Natural Resources, Environment and Rural Poverty Division, Country Department 1,

Latin America and the Caribbean Region, Washington, D.C., USA.


24/52

18


25/52

19

Despite the relative simplicity of composting, its suitability for developing countries, and its com-

pelling economic and environmental benefits, several projects initiated over the past decades have

failed due to technical, financial, and institutional reasons. Few urban areas have been able to

successfully operate composting plants due to a combination of the following:

inappropriate technology

poor quality feed stock waste

lack of operator education and training

mechanical breakdown

poor maintenance high operating costs

offensive odor emissions

poor marketing plans for the end product

insufficient focus on management

lack of cooperation from the public and municipal governments

Transfer of solid waste technology, including processes and equipment, is usually from industrial-

ized countries to less developed countries. Often the technology is not directly applicable, as it fails

to adequately consider local factors such as the waste characteristics, seasonal variations in climate,

lack of technical education and training, cultural attitudes towards solid waste, and the status of

waste management in political institutions.

The preference of mechanized composting technology over labor intensive processes is usually

inappropriate for developing countries. A lack of trained and educated personnel to control the

daily operations results in a low-quality end product and frequent mechanical breakdowns. When

a piece of equipment becomes inoperable from misuse or poor maintenance, it is often too expen-

sive and time consuming to purchase and import foreign spare parts.

Many composting facilities are designed to process high-quality waste consisting primarily of or-

ganic matter. Often the waste arriving at the plant is mixed municipal solid waste which requires

more energy to process, causes mechanical breakdowns, and reduces the quality of the final com-

post. Source separated organic waste is the preferred feed stock since contamination by plastics,

glass, metals, and household hazardous materials is minimized. The principle source of heavy

metals in MSW is often common household products: batteries (mercury, cadmium, lead, zinc),leather (chromium), paints (chromium, lead, cadmium), plastics (cadmium, lead, nickel), light

bulbs (lead), paper (lead), consumer electronics (lead, cadmium), ceramics (lead, cadmium), cos-

metics (cadmium, zinc), and dust from sweeping (de Bertoldi, 1993; Richard, 1993). However, the

biggest source of contamination in cooler climates is usually coal-ash (from home heating).

Municipalities often give solid waste management a low priority in terms of financial and institu-

tional support. Lack of coordination between composting facilities and solid waste management


26/52

20

authorities, inadequate financial resources, absence of technical guidance, and poor marketing plans

are common problems experienced by composting operations in many developing countries. Tech-

nical problems and poor management invariably lead to higher production costs and ultimately

financial losses. For example, a composting plant operating in Delhi experienced an increase in

production costs from Rs. 384 per tonne in 1983 to Rs. 2,091 in 1991. A corresponding increase in

the selling price of the compost was only marginal because of low product demand (Selvam, 1996).

Box A1. Vermicomposting in IndonesiaVermicomposting is a successful method to process organic waste in densely populated,low-income neighborhoods in Indonesia. A pilot group of about 60 Jakarta families use 30L tubs with 0.5 kg of worms to compost household organic material. After one to twomonths, a tub can produce 20 kilograms of vermicompost which is used by the family orsold locally to supplement the household income (Perla, 1997).

Box A2. Apartment composting in IndiaPatna, India has a population of about one million with little door-to-door waste collectionnor any composting facilities or sanitary landfills. On average a three person householdgenerates 2.1 kg of food waste each week. Backyard composting is used by some house-holds, but this is not an option for those living in apartments. A composting method wasdeveloped for apartment dwellers to use their balconies and window sills. Excess water isdrained from the organic waste and placed in clay pots. Soil supplemented with floor sweep-ings and dried moss from roof tops is added to equal amounts of waste. The compostmatures in 3 to 4 months and is used directly for planting without further additions offertilizer of chemicals. Flowers, ornamental plants, spinach, and tomatoes are success-fully grown in the compost (Mazumdar, 1992).

Asomani-Boateng et al.(1996) describe how several African countries built sophisticated, highly

mechanized MSW composting plants with the aid of foreign capital and assistance during the

1970s and 1980s. Lack of equipment and technical personnel, mechanical breakdowns, and finan-

cial restrictions resulted in these facilities becoming largely inoperable.

In 1974, the Government of India began a modified scheme to revive MSW composting by focusing

on cities with a population over 300,000. Recognizing the link between waste collection, composting

and agriculture, the Ministries of Agriculture and Urban Development each reimbursed percent-

ages of composting capital and operating costs. During a ten year period, eleven mechanical

composting facilities, with processing capacities ranging from 150 to 300 tons of MSW per day,

were established in cities like Bombay, Delhi, Kanpur, Bangalore, Jaipur, and Calcutta. Today,

with the exception of Delhi and Bangalore, all of the plants have been shut down due to poor qualitysolid waste, wrong choice of equipment, poor maintenance, higher production costs and financial

losses, low priority at the top level, and poor marketing efforts (Selvam, 1996).

A 1990 survey conducted in Brazil discovered that 57 municipalities had composting facilities, of

which only 18 were operating and 15 were under construction. The other 24 plants were closed as

the result of operational or financial failures. Composting was promoted by BNDES, a special fund

for recycling or composting plants which was available to municipalities, autonomous agencies, or

concessionaires. Funds were channeled to contractors whose technical and marketing assumptions


27/52

21

were not always appropriate for municipal needs and specifications. Municipal managers were

often frustrated by an erroneous vision of generating a profit on the composting operation or by the

inability to produce compost of the quality necessary for the market. Not only did small municipali-

ties experience difficulties with composting, the city of Rio de Janeiro apparently spent US$30

million on a 1,200 tons per day composting plant commissioned in 1993. The plant was shut down

one year later because of operational and odor problems, and it remains closed today (World Bank,

1997b).

Box A3. Community composting in BrazilIn Olinda, two neighborhoods have set up composting units on plots of land of about 250m2. Incoming waste is dumped into a shallow, lined pit and lifted onto a sloped sortingtable where rejects and recyclable materials are removed. A team of six individuals cansort one trailer load of waste, weighing approximately 600 kg, in about 45 minutes. Theremaining organic matter is weighed and formed into windrows. The composting process

is controlled by measuring the temperature on a daily basis and the windrows are turnedwhen the temperature drops or when it rises above 65oC. Pieces of plastic and other rejectmaterial that were missed during pre-sorting are removed when the windrows are turned.Stabilized compost is sieved before it is transferred to stockpiles for future use. Regularsupervision of the composting process is necessary to ensure proper control (Lardinoisand van der Klundert, 1993).

Despite the numerous examples of Brazilian composting plants that have failed, the Municipality

of Sao Paulo has managed to run a large successful composting operation since the early 1970s.

Two materials sorting and composting plants are located in Vila Leopoldina and Sao Mateus. Each

plant has been modified and enlarged by the municipality since the installation and currently havecapacities of 900 and 600 tons per day, respectively.

A study of the efficiency of the Sao Mateus plant reported that for each ton of waste processed, the

output is made up of 53% compost, 4% recyclable material, and 43% rejects that are disposed in

sanitary landfills. After taking into consideration the income from compost sales (US$5.80 per ton

of compost, or US$3.08 per ton of waste processed) and recyclable sales, the municipality is re-

quired to subsidize the operation at a cost of US$10.76/ton of waste processed (World Bank, 1997b).

Box A4. Household source separation in EgyptEfforts are underway to convince Cairo residents of the benefits of separating their wastes

into organic and non-organic fractions. In an experimental project, 600 households areseparating their residential wastes into two streams before collection. The health andefficiency of the waste collectors and the quality of the compost are being monitored. Thecollectors and processors realize numerous benefits from source separation: reduced inci-dence of worker injuries and waste related diseases, higher selling price of cleaner recy-clable materials, less time required to sort the incoming waste materials, and improvedcompost quality. Municipal waste management authorities also benefit from householdsource separation because less waste has to be collected resulting in lower transportationand disposal costs (Lardinois and van der Klundert, 1993).


28/52

22

Settlements of landless family groups, known as the Zabbaleen, located on the outskirts of Cairo

rely on the collection and sorting of urban solid waste as a source of income. Maqattam is the

largest of the Zabbaleen settlements with a population of seventeen thousand people. In the early

1980s, a community composting operation began at a former quarry in the Maqattam settlement to

compost garbage from which recyclables have been removed and pig manure from the zeribas.

Lardinois and van der Klundert (1993) report that the waste is dumped by a mechanical front-end

loader through a grid onto a conveyor belt, which transfers the organic material to a hopper and

finally to a rotating, cylindrical drum, where the material is sieved. The composting time varies

from only six to fifteen days since the waste has already undergone partial decomposition. Me-

chanical parts for the plant can be purchased in Egypt, but some electrical parts have to be im-

ported.

The final compost is sold to local farmers to improve the quality of existing agricultural soils. Even

though the overall quality of the compost appears to be good, small pieces of glass and plastics and

significant quantities of heavy metals have been observed in the final product. According to SEEDS

(1997), the total cubic metric tonnage of compost produced and sold has steadily increased since

1988. The resulting profits cover the operating costs of the plant and supports staff from the

Association for the Protection of the Environment (APE) who oversee social development compo-

nents of the project (functional literacy, health, and income generating initiatives).

Cipinang Besar, a neighborhood in East Jakarta, decided to implement a community composting

program to properly dispose of household wastes being dumped into the Cipinang River. Indis-criminate dumping clogged the river and canal and caused flooding during the rainy season. Finan-

cial assistance from the United Nations Development Program (UNDP) and the government of

New Zealand helped the community to establish its own composting business in 1992. The facility

was built from recycled scrap steel, currently employs 12 people, and produces 3 tons of compost

per month. Control of the composting business empowers the community and addresses their

specific social and environmental needs (Perla, 1997).

The Watam community composting project began in 1990 with support from the Indonesian Center

for Policy and Implementation Studies (CPIS) and the local municipality. The project is located on

a rent free site adjacent to the municipal transfer station which serves 3,000 families, a park and a

market. The facility consists of a cement pad constructed for windrows, curing, screening and

storage; a roof shelter to protect the process from rain; and four foot high enclosing walls. A yearprior to operation, managers were educated and trained in compost technology, environmental

controls, health issues, and business management. Workers also completed a 3 month training

program on the composting process and related health risks. Compost produced by the Watam

facility was marketed to a nursery chain selling plants and fertilizer to middle- and high-income

households and a golf course for landscaping. The project lost its distributor and is now running at

half capacity because it is unable to sell the compost (Perla, 1997).


29/52

23

CPIS initially conducted heavy metal tests on the final compost produced by projects it was fund-

ing. The results did not show high levels of metals and the compost met 1991 U.S. Environmental

Protection Agency (EPA) standards. Untreated compost leachate draining into the Ciliwung River

was found to actually contain less pollutants than the river water. Worker health has also been

monitored and no adverse effects have been reported (Perla, 1997).

Founded in 1981, the Bhawalkar Earthworm Research Institute (BERI) has established six large-

scale vermicomposting projects and motivated almost 5,000 farmers to use vermicomposting appli-

cations. A system implemented by BERI at the Indian Aluminum Co. Ltd. (Indal) site uses worms

to treat solid waste and sewage from a colony of 500 homes and to filter the companys canteen

greywater so that it can be reused in the cooling tower. Venkateshwara Hatcheries Ltd. applies

BERI vermiculture to process almost 4 tonnes per day of poultry residues and manure. The endproduct is marketed as Biogold and sold at a much higher price than conventional compost. A

vermiculture facility is successfully operated by Orient Vegetexpo Ltd. to digest 4.5 tonnes of onion

residuals per day during a ten month processing season. The adsorptive properties of vermi-

composting is able to dissipate the smell of onions within a few hours of feeding (White, 1996).

In response to a lack of proper sanitation leading to the spread of water-borne diseases, the Alterna-

tive Technology Group (GTA) developed the Integral System for Recycling Organic Wastes (SIRDO)

to treat household wastewater, human excreta and organic matter in rural and urban environments.

The end product can be used beneficially within the community, or it can be marketed for applica-

tion to agricultural soils. SIRDO technology is appropriate for the conditions of developing coun-tries because the units:

provide decentralized waste treatment

encourage household source separation and waste recycling

reduce waste collection, transportation and disposal requirements

prevent contamination of surface and ground waters

reduce infrastructure requirements (piping, pumping)

adapt to both rural and urban environments

create a beneficial end product

do not require mechanization or water

A dry SIRDO unit can be built with one or two chambers and takes approximately 6 months to fill

one chamber with human excreta and organic matter, which is then kept closed for an additional 6months. Solar energy is used to enhance the natural aerobic decomposition of the organic wastes.

Sufficiently high temperatures should be achieved within the chamber during the final 6 months to

eliminate most pathogens from the final compost (GTA, 1992).

SIRDO technology has been refined over the years and is able to treat human and organic wastes.

However, examples of SIRDO being implemented in urban communities of Merida and the Valley


30/52

24

of Mexico illustrate how political, social, and administrative problems can detract from its success-

ful operation. Strong opposition was experienced at both sites when the system was first intro-

duced. A community-based project like SIRDO worries some government officials that urban popu-

lations will become less dependent on state support, thereby leading to more political indepen-

dence. Many local residents initially did not accept the SIRDO units because they faced a new

technology that they did not understand and were required to modify some of their daily habits. A

local cooperative was formed in Merida to operate and maintain the units, provide education to

community members, and market the final product. The cooperative was initially successful; how-

ever, financial conflicts arose which stopped the production of fertilizer and related income-gener-

ating activities in the community (SEEDS, 1984).

A Bombay based agrochemical manufacturing industry, Excel Industries Ltd., is implementingsemi-mechanical MSW composting facilities in various Indian cities. In the past 4 years, five

plants have been set up in Bombay, Ahmdabad, Gwalior, Bhopal, and Vijayawada; the largest plant

located in Bombay with an installed capacity of 500 tons per day. Excel Industries usually runs its

plants on a build, own, operate basis and encourages local partners to take over and operate the

plant for a fee.

The final compost product is marketed to farmers under the name of Celrich bio-organic soil en-

richer. The compost has a lower nutrient value and is more expensive than government subsidized

chemical fertilizers; however, farmers understand the benefits of applying compost to their crops.

Excel Industries has a nation-wide distribution and sales network for its agrochemicals which pro-

vides a marketing and circulating advantage for its Celrich compost to agricultural regions. Ac-

cording to Excel Industries Ltd., approximately 95 percent of their compost is purchased by farmersfor growing sugarcane, grapes, bananas, etc. that has resulted in a 25 percent decrease in chemical

fertilizer use among these farmers.

According to Excel Industries estimates, a 500 ton per day composting plant requires a capital

investment of Rs. 60 million, or US$1.7 million at January 1996 price level, excluding the cost of

land. This estimate includes a 5 percent turnkey know-how fee and commissioning charges and

about 8 to 10 percent for working capital. The overall production cost of the compost is about Rs.

1,200 to 1,400 per ton. The selling price ranges between Rs. 1,600 to 2,000 per ton of compost

subject to transportation distances and other local overheads (Selvam, 1996).


31/52

25

All life is dependent on nutrient cycling since growth needs decay. Composting is simply theenhancement of the natural biological degradation of organic matter. Microorganisms con-vert the organic matter into a humus-like material; the end product being more commonlyknown as compost. The following general formula and Figure B1 illustrate the inputs andoutputs for the conversion of organic matter in the presence of oxygen:

bacteria resistantorganic + 0

2+ nutrients -------> new cells + organic + CO

2+ H

20 + NH

3+ SO

42-+...+ heat

matter matter

(Tchobanoglous et al., 1993)

Composting is an aerobic process that by definition requires oxygen. The consumption ofoxygen is greatest during the early stages and gradually decreases as the process continues tomaturity. Limiting the oxygen supply to the organic materials slows down the composting

process, creating anaerobic conditions and potential odors. Different anaerobic reactions by

microorganisms form intermediate decomposition compounds such as methane, hydrogensulfide, and organic acids.

Physically turning the compost or providing forced aeration maintains aerobic conditionsand limits odors. Excessive temperatures also indicate that the materials are not receivingadequate airflow. The turning frequency is dependent on the type of system and the length oftime to make compost, as shown in Table B1.


32/52

26

System Intensity Height of Pile Width of Pile Turning Time to Create

(meters) (meters) Frequency Final Product (months)

Minimal 3.0-3.7 6.1-7.3 1 time per year 24-36

Low 1.5-2.1 3.7-4.3 3-5 times per year 14-18

Intermediate 1.5-2.4 3.7-5.5 Weekly 4-6

High 2.4-3.0 4.9-6.1 Aerated static pilea 3-4

aForced aeration is used for a period of 2 to 10 weeks, after which the piles are occasionally turned.(Tchobanoglous et al., 1993)

Moisture dissipates heat and serves as a medium to transport critical nutrients. Moisture content

varies with the particle size and physical characteristics of the raw materials; the preferred moisture

content for composting is between 50 and 60 percent. A low moisture content, usually below 40

percent, will slow the composting process whereas a high moisture content, usually above 65 per-

cent, will restrict air movement through the pore spaces and result in anaerobic conditions (Lardinois

and van der Klundert, 1993). Excess leachate may also be produced if the moisture content is too

high. Moisture levels should be maintained so that materials are thoroughly wetted without being

waterlogged. Generally, the materials are too wet if water can be squeezed out of a handful and too

dry if the handful does not feel moist (Rynk, 1992).

The primary nutrients required for microorganism growth are carbon, nitrogen, phosphorous, and

potassium. Bacteria also need trace amounts of sulfur, sodium, calcium, magnesium, and iron

which are usually present in adequate quantities in the organic material.

Of the primary nutrients, carbon and nitrogen play the most important role in the composting

process. Carbon is used by microorganisms for energy and growth whereas nitrogen is needed for

protein and reproduction. The amounts of carbon and nitrogen relative to one another are referred

to as the carbon-to-nitrogen ratio (C/N ratio). A C/N ratio ranging from 20/1 to 25/1 is optimum

for composting organic wastes, but higher ratios may be possible. Table B2 indicates various C/N

ratios of compostable materials. The optimum C/N ratio can be attained by combining various

organic wastes. For example, leaves (high in carbon, low in nitrogen) can be blended with food

waste (high in nitrogen) to balance the C/N ratio.


33/52

27

Material Percent N C/N Ratio1

Food processing wastes

Fruit wastes 1.52 34.8

Mixed slaughterhouse waste 7.0-10.0 2.0

Potato tops 1.5 25.0

Manures

Cow manure 1.7 18.0

Horse manure 2.3 25.0

Pig manure 3.75 20.0

Poultry manure 6.3 15.0Sheep manure 3.75 22.0

Sludges

Digested activated sludge 1.88 15.7

Raw activated sludge 5.6 6.3

Wood and straw

Lumber mill wastes 0.13 170.0

Oat straw 1.05 48.0

Sawdust 0.1 200.0-500.0

Wheat straw 0.3 128.0

Wood (pine) 0.07 723.0

Yard wastes

Grass clippings 2.15 20.1

Leaves (freshly fallen) 0.5-1.0 40.0-80.0

Biomass

Water hyacinth 1.96 20.9

Bermuda grass 1.96 24.0

1C/N ratio is based on total dry weights.(Tchobanoglous et al., 1993)

Generally, all of the organic nitrogen present in organic compounds will biodegrade, whereas only

a portion of the organic carbon may biodegrade. For this reason, the C/N ratio should be based on

the total dry bio-available weights of carbon and nitrogen.


34/52

28

Microorganisms are an essential component of the composting process since they are responsible

for the biological conversion of the organic matter. The primary microorganisms involved are

bacteria, fungi, and actinomycetes and can be further classified according to the temperature ranges

described in Table B3.

Type Temperature (oC)

Range Optimum

Psychrophilic -10-30 15

Mesophilic 20-50 35

Thermophilic 45-75 55

(adapted from Tchobanoglous et al., 1993)

Different microorganisms contribute to the decomposition of organics at various stages in the

composting process. Microorganism growth and decay over the composting period is shown in

(Riffaldi et al., 1986 and de Bertoldi et al., 1983)(1) Mesophilic microorganisms break down simple sugars

(2) Thermophilic microorganisms break down proteins and more complex carbohydrates

(3) Mesophilic bacteria, fungi, and actinomycetes attack complex compounds (e.g. cellulose and lignin); C/N, temperature and

moisture decline

(4) Phytotoxic

(5) Peak activity for nitrogen fixing bacteria

(6) Humification of organic matter by actinomycetes


35/52

29

Occasionally innoculums or special additives are touted as ways to speed up the composting

process. Almost always these claims are false. There is sufficient background bacteria to start the

composting process, especially if a small portion of finished compost is initially added to the or-

ganic matter. The availability of oxygen, C/N ratios, moisture content, and temperature are the

principal determinants of the process rate.

Microorganism activity releases energy in the form of heat which is dissipated by water evapora-

tion. The temperature rapidly rises in the initial composting stages and eventually decreases as the

biodegradable organic carbon is consumed. As illustrated in Figure B3, the temperature profile

varies between the windrow and aerated static pile processes in the thermophilic phase.


Optimum composting generally occurs in the mesophilic and thermophilic temperature ranges.

Higher temperatures are required to kill pathogens, weed seeds, and fly larvae within the compost.

However, excessive temperatures will slow the composting process by causing many of the composting

microorganisms to become dormant or die off. Table B4 indicates the temperature exposures re-

quired to eliminate certain pathogens and parasites from the compost.


36/52

30

Microorganism Observations

Salmonella typhosa Growth ends at 46oC; death within 30 minutes at

55-60oC and within 20 minutes at 60oC

Salmonella sp. Death within 1 hour at 55oC and within 15-20

minutes at 60oC

Escherichia coli Most die within 1 hour at 55oC and within 15-20

minutes at 60oC

Entamoeba histolytica cysts Death within a few minutes at 45oC and within a

few seconds at 55oC

Taenia saginata Death within a few minutes at 55oC

Trichinella spiralis larvaeQuickly killed at 55

o

C; instantly killed at 60

o

CBrucella abortus or Br. Suis Death within 3 minutes at 62-63oC and within 1

hour at 55oC

Micrococcus pyogenes var. aureus Death within 10 minutes at 50oC

Streptococcus pyogenes Death within 10 minutes at 54oC

Mycobacterium tuberculosis var. hominis Death within 15-20 minutes at 66oC or after

momentary heating at 67oC

Corynebacterium diphtheriae Death within 45 minutes at 55oC

Necator americanus Death within 50 minutes at 45oC

Ascaris lumbricoides eggs Death in less than 1 hour at temperatures over 50oC


An effective compost operator is able to balance the need for higher temperatures to suppress patho-

gens with the potential to over-heat the composting mass, thereby slowing the process. A general

rule of thumb for pathogen suppression is to maintain the compost process at 55 to 65 oC for 3

consecutive days.

Composting can occur over a broad pH range due to the variety of microorganisms involved; how-

ever, the preferred pH level is between 6 and 8. Fluctuations in pH result from the formation of

organic acidic compounds or the production of ammonia. Regardless of the initial pH and fluctua-

tions, the final end product will have a stable pH around 7.

Porosity, structure, texture, and particle size all influence the composting process. Porosity is a

measure of the air spaces within the pile and affects airflow; structure refers to the rigidity of the

particles and the ability to prevent settling and compaction; and texture describes the available

surface area for microbial activity (Rynk, 1992).


37/52

31

The optimum particle size is dependent upon the raw material, although a smaller particle size will

increase the rate of aerobic decomposition since the available surface area is increased. Depending

on the composition of the raw material, size reduction can be achieved by manual and mechanical

methods such as screening, grinding, or chopping. Typical particle sizes should be approximately

1 cm for forced aeration composting and 5 cm for passive aeration and windrow composting (Obeng

and Wright, 1987).

Bulking agents can be added to the raw material if it lacks the structure to maintain adequate

porosity within the compost pile. Wood chips, recycled compost, peat moss, corn cobs, crop resi-

dues, bark, leaves, shellfish shells, waste paper, and shredded tires are all examples of good bulking

agents. Most of these materials are recovered from the final compost by screening and recycled.

Curing is an often neglected stage in the composting process. This final stage prevents the use of

immature compost by allowing the compost to mature until stable. Curing occurs at lower tempera-

tures, consumes less oxygen, generates less heat, and reduces moisture evaporation. This stage

continues the aerobic decomposition of resistant compounds, organic acids and large particles,

increases the concentration of humus, and allows the compost to gain disease suppression qualities

(Rynk, 1992). Immature compost is an undesirable end product because it continues to consume

oxygen, contains high levels of organic acids, possesses a high C/N ratio, competes for nitrogen,

and can damage plant growth when used for agricultural applications.

The curing stage does not have a distinct beginning or end. In the windrow process, curing starts

when the temperature does not re-heat after turning and begins in forced aeration systems after the

temperature decreases to the mesophilic range. The compost becomes mature as the temperatureapproaches ambient conditions.

Mature compost should meet the following parameters to ensure that it is stable:

should have a C/N ratio of less than 22 to be safe for agricultural use

should not re-heat over 20oC upon standing

should reduce volume of raw organic material by at least 60 percent

Conditioning improves the final quality and appearance of the mature compost. Manual or me-

chanical screening is an effective way to remove unwanted objects, recover bulking agents, and

separate organics that are not completely decomposed. Screening also provides different gradesof compost based on the particle size; coarse compost is usually returned back to the process to be

further refined.


38/52

32


39/52

33

Windrow composting is a simple and versatile method where organic matter is built into large piles

and physically turned on a regular basis. Regular turning of the windrows helps oxygenate the pile;

breaks up particles to increase surface area; improves the porosity to prevent settling and compac-

tion; and allows trapped heat, water vapor, and gases to escape. A turning schedule should be

established based on the rate of decomposition, moisture content, porosity of the material, and the

desired composting time (often a function of land availability). The frequency of turning the wind-

row should be adjusted as the rate of decomposition decreases with time.

The size, shape, and spacing of the windrows depends on the equipment used for turning. Forexample, bucket loaders are used to build high windrows whereas turning machines create low and

wide windrows. Manual labor is also used for windrows of a smaller scale when the additional cost

and use of machinery is not feasible.

The porosity of the raw material affects the air flow within the windrow. Dense materials, such as

manure, require smaller windrows to minimize anaerobic zones, whereas more porous and lighter

materials, such as leaves, can be built into larger windrows. A balance needs to be achieved be-

tween proper aeration and temperature requirements since small windrows tend to dissipate heat

quickly and may not reach adequate temperatures to kill pathogens and weed seeds (Rynk, 1992).

This method is very similar to windrow composting except that turning is not required for aeration.

Air is supplied to the organic material through perforated pipes embedded in the pile. The chimney

effect created by the warm gases rising out of the windrow causes air to flow through the pipes. A


40/52


34



porous base

Compost en Paises en Desarrollo

Documents

Transcript of Compost en Paises en Desarrollo